EQ Tues 4/30 What is the difference in connecting components in a circuit in series or in parallel? Series Parallel Circuits Notes Homework: Page 619 Q 1-4 Pg 623 Q 11 Pg 626 Q 15,16

EQ Thursday 4/26 How does the way you hook up a resistor effect the current? Series and Parallel Circuits Notes

Schematic Symbols Before you begin to understand circuits you need to be able to draw what they look like using a set of standard symbols understood anywhere in the world For the battery symbol, the LONG line is considered to be the POSITIVE terminal and the SHORT line , NEGATIVE.

The Voltmeter and Ammeter Current goes THROUGH the ammeter Since a voltmeter measures voltage or POTENTIAL DIFFERENCE it must be placed ACROSS the device you want to measure. That way you can measure the CHANGE on either side of the device. Voltmeter is drawn ACROSS the resistor Since the ammeter measures the current or FLOW it must be placed in such a way as the charges go THROUGH the device.

Ways to Wire Circuits There are 2 basic ways to wire a circuit. Keep in mind that a resistor could be ANYTHING ( bulb, toaster, ceramic material…etc) Series – One after another Parallel – between a set of junctions and parallel to each other

Series Circuit In Series : More resistors = less current In in series circuit, the resistors are wired one after another. Since they are all part of the SAME LOOP they each experience the SAME AMOUNT of current any where in the circuit. In figure, however, you see that they all exist BETWEEN the terminals of the battery, meaning they SHARE the potential (voltage). In Series : More resistors = less current

In Series : the voltage across each resistor adds up to the total voltage As the current goes through the circuit, the charges must USE ENERGY to get through the resistor. So each individual resistor will get its own individual potential voltage). Note: We use the terms “effective” or “equivalent” to mean TOTAL!

Example A series circuit is shown to the left. What is the total resistance? What is the total current? What is the current across EACH resistor?   What is the voltage drop across each resistor?( Apply Ohm's law to each resistor separately) R(series) = 1 + 2 + 3 = 6 Ω V=IR 12=I(6) I = 2A They EACH get 2 amps! V1Ώ=(2)(1)= 2 V V3Ω=(2)(3)= 6V V2Ω=(2)(2)= 4V ***the individual VOLTAGE DROPS add up to the TOTAL!!

Parallel Circuit In a parallel circuit, we have several branches. the current splits up among the branches the individual branch currents add up to the total current It is important to understand that parallel circuits will all have some position where the current splits and comes back together. We call these JUNCTIONS. The current going IN to a junction will always equal the current going OUT of a junction. Junctions

Parallel Circuit Notice that the JUNCTIONS both touch the POSTIVE and NEGATIVE terminals of the battery. That means you have the SAME potential difference down EACH individual branch of the parallel circuit. This means that the individual voltages drops are equal. DV This junction touches the POSITIVE terminal This junction touches the NEGATIVE terminal ***The reciprocal of the equivalent resistance in parallel is calculated by the sum of the reciprocals of all resistors

Add two 100 ohm resistors in parallel The equivalent resistance of 2 identical resistors in parallel = ½ of one of them The equivalent resistance of 3 identical resistors in parallel = 1/3 of one of them As more resistors are added in parallel the equivalent resistance goes down and the current goes up!

Example To the left is an example of a parallel circuit. a) What is the total resistance?   b) What is the total current?   c) What is the voltage across EACH resistor?   d) What is the current drop across each resistor? (Apply Ohm's law to each resistor separately) 2.20Ω 3.64 A 8 V each! Notice that the individual currents ADD to the total. 1.6 A 1.14 A 0.90 A

EQ Determine the equivalent resistance of the two 5Ω resistors in parallel and two 4Ω resistors in series Today: Complex Circuits (Notes part2) Circuits practice Q due Tuesday *** Review Thurs - TEST FRIDAY

each resistor has 20 ohms below: A compound circuit has resistors connected in series and parallel- 1. combine any in series – on the same branch 2. combine any in parallel 3. combine the Req from parallel to Req from series

Compound (Complex) Circuits Solve this type of circuit from the inside out. WHAT IS THE TOTAL RESISTANCE?

Compound (Complex) Circuits Suppose the potential difference (voltage) is equal to 120V. What is the total current? 1.06 A What is the VOLTAGE DROP across the 80W resistor? 84.8 V

Compound (Complex) Circuits What is the current across the 100W and 50W resistor? What is the VOLTAGE DROP across the 100W and 50W resistor? 0.352 A Add to 1.06A 35.2 V Each! 0.704 A

EQ FRI 4/27 how does the arrangement of resistors effect the current in a series or a parallel circuit? Practice problems ( on your own paper) Glencoe book draw a sketch and show all work Page 619 Q 1-4 Page 623 Q 11 Page 626 Q 15 – 16 ( top)

EQ Wed 5/2: Look over the review TO BE HANDED IN: 1- Ohm’s Law lab 4/24 2- Ohm’s Law worksheet 4/25 3 - Series Parallel Circuits Notes 4/26-30 4- Text practice problems4/27 5- Circuits test review worksheet 5/1 Progress reports – get signed